Cable television (CATV), originally introduced in the late 1940's as a way to transmit television signals by coaxial cables to houses in areas of poor reception, has over the years been modified and extended to enable the cable medium to transport a growing number of different types of digital data, including both digital television and broadband Internet data.
One of the most significant improvements occurred in the 1990's, when a number of major electronics and cable operator companies, working through CableLabs®, a non-profit R&D consortium, introduced the Data Over Cable Service Interface Specification (DOCSIS). First introduced in the late 1990's as DOCSIS version 1.0, and upgraded many times since (currently at DOCSIS version 3.0), the DOCSIS standard defines the Physical Layers (PHY) and Media Access Control (MAC) layers needed to send relatively large amounts of digital data through coaxial cables that were originally designed to handle analog standard definition television channels.
Originally, analog television (in the US) transmitted television channels as a series of roughly 6 MHz bandwidth radiofrequency waveforms at frequencies ranging from about 54 MHz (originally used for VHF Channel 2) up to about 885 MHz for now no-longer used UHF channel 83. This television signal was transmitted as a combination amplitude modulated signal (for the black and white portion), quadrature-amplitude modulated signal (for the color portion), and frequency modulated signal (for the audio portion), and this combined signal will be designated as a Frequency Division Multiplexed (FDM) signal.
With the advent of digital television and high definition television standardization in the late 1980's and early 1990's, the basic 6 MHz bandwidth spectrum of analog television was retained, but the modulation scheme was changed to a more sophisticated and higher data rate Quadrature Amplitude Modulation (QAM) scheme, which can encode digital information onto a very complex QAM analog signal (waveform).
The DOCSIS standard built upon this analog and digital TV foundation, and specified additional standards to provide broadband Internet services (Internet protocols, or IP), voice over IP, custom video on demand, and other modern services based upon the QAM data transmission waveforms (generally also 6 MHz wide) previously established for digital and high definition television.
As a result, by a series of steps, simple coaxial cables, originally run at great expense to millions of households starting from the 1950's and 1960's, has been gradually upgraded to accommodate ever increasing demands for digital data. At each house (or apartment, office, store, restaurant or other location), the household connects to the CATV cable by a cable modem, uses the cable modem to extract downstream DOCSIS digital data (frequently used for high-speed Internet), and inject upstream DOCSIS digital data (again frequently used for high-speed Internet applications).
Unfortunately, even in a coax cable, there is a finite amount of bandwidth available to transmit data. Coax cables and their associated radiofrequency interface equipment have typically only used the frequency range under about 1000 MHz, and so there are limits to how much data the 1950's era coaxial cable can ultimately transmit.
By contrast, optical fiber (fiber optics, fiber) technology, which uses much higher optical frequencies (with wavelengths typically in the 800-2000 nanometer range), can transmit a much higher amount of data. Optical fiber data rates typically are in the tens or even hundreds of gigabits per second. Indeed, the entire RF CATV cable spectrum from 0 to 1000 MHz can be converted to optical wavelengths (such as 1310 nm or 1550 nm), be carried over an optical fiber, and then be converted back to the full RF CATV cable spectrum at the other end of the fiber, without coming close to exhausting the ability of the optical fiber to carry additional data.
This conversion process can be achieved by relatively simple optical to digital or digital to optical converters, in which the CATV RF waveforms are simply converted back and forth to a light signal by simple (“dumb”) E/O or O/E converters, located in nodes that connect optical fibers to CATV cable (fiber nodes).
The higher data carrying capacity of optical fibers allows additional data to be carried as well, and in some schemes, the essentially analog (digital encoded in analog) spectrum of CATV waveforms is carried at one optical wavelength (such as 1310 nm), and digital data encoded by entirely different protocols may be carried at an alternate optical wavelength (such as 1550 nm). This dual scheme is often referred to as wavelength-division multiplexing.
Optical fiber technology has been widely used for high capacity computer networks, and these networks often do not use the DOCSIS protocols or QAM protocols to transmit data. Rather, these high capacity computer networks often use entirely different types of data transmission protocols, such as the Ethernet protocols IEEE 802.3ah, 1000BASE-LX10, 1000Base-BX10, and others. These networks and protocols are often referred to as GigE networks, which is an abbreviation of the Gigabyte speeds and Ethernet protocols used for fiber based computer network.
Thus if a user desires to transfer computer data from RF QAM waveforms transported over a CATV cable to a high speed GigE fiber network, the data must be transformed back and forth between the DOCSIS cable QAM waveforms and the alternate protocols (often Ethernet protocols) used in fiber GigE networks.
Although ideally, the best way to satisfy the ever increasing household demand for digital data (e.g. video—on demand, high speed Internet, voice over IP, etc.) would be by extending optical fiber to each household, this would be an incredibly expensive solution. By contrast, cable based CATV solutions have already been implemented for tens of millions of households, and this expense has already been borne and amortized over decades of use, starting from the 1950s. As a result, it is far more economically attractive to find schemes enable the existing, if bandwidth limited, CATV cable system, to be further extended to meet the ever growing demands for additional data.
Cable System Components:
At the “head” end (application Ser. No. 12/692,582 occasionally also used an alternative term “plant” as in the sense of a “place where an industrial process takes place” to also designate the head end, but here the more standard CATV term “head” is generally used throughout) of a typical CATV cable network (cable), the challenging task of combining the many different types of data (analog television channels, digital television channels, on-demand channels, voice over IP, DOCSIS channels, etc.) and sending this data to users (households) scattered through many different neighborhoods in various regions of towns, cities, counties and even states is handled, in part, by Cable Modem Termination Systems (CMTS) devices. These CMTS devices connect to the various data sources (television stations, video servers, the Internet, etc.) at one end, and to many different CATV cables at the other end.
Typically the head end CMTS device will have a connection to the various data sources and appropriate data switches (such as a Level 2/3 switch) at one end, and often a plurality of different line cards (often physically packaged to look like blade servers, and put into a main CMTS box that holds multiple line cards) at the other end. Each line card will typically be connected to either cables or optical fibers that travel away from the cable head towards various groups of multiple neighborhoods, where typically each group of multiple neighborhoods will be in a roughly contiguous geographic region. The head end line card cables or optical fibers are then typically subdivided further by various splitters and nodes, and eventually the signals flow to the individual neighborhoods, each served by its own CATV cable.
At the neighborhood level, an individual CATV cable will serve between about 25 and a few hundred households (houses, apartments). These connect to the individual cable by cable modems. Here each cable modem will be considered to be a household or “house”, regardless of if the cable modem serves a house, apartment, office, workplace, or other application.
The CMTS line cards, which according to prior art are located at the head end, will typically contain at least the MAC and PHY devices needed to transmit and receive the appropriate CATV signals. Typically the line card PHY devices will contain a plurality of QAM modulators that can modulate the digital signals that a Level 2/3 switch has sent to that particular line card, and send the signals out over cable or fiber as a plurality of QAM channels. The line cards will also typically contain MAC and PHY devices to receive upstream data sent back to the cable head from the various cables and cable modems in the field.
It is impractical to directly connect each individual neighborhood CATV cable directly to the cable plant. Rather cable networks are arranged in more complex schemes, where the signals to and from many different individual neighborhoods are combined by the network prior to reaching the cable plant or cable head. Thus each CMTS line card will typically send and receive signals to and from multiple neighborhoods.
Instead of sending and receiving data by cable, the various CMTS line cards can instead communicate to their various groups of neighborhoods by optical fiber. However it is also impractical to run individual fibers directly from individual neighborhoods to the cable plant or cable head as well. Thus fiber networks are also usually arranged in more complex schemes, where the signals to and from different individual neighborhoods are also combined by the optical fiber network before the signals reach the cable plant or cable head.
At a minimum, the optical fiber network will at least typically split (or combine) the fiber signals, often by “dumb” optical fiber splitters/combiners (here called splitters) that do not alter the fiber signal, and the split signal then will be sent by sub-fibers to the various neighborhoods. There, the optical fiber signal can be converted to and from a RF signal (suitable for the individual cable) by a “dumb” fiber node that itself simply converts the optical to RF and RF to optical signals without otherwise altering their content. These hybrid optical fiber to cable networks are called Hybrid Fiber Cable (HFC) networks.
Prior art work with various types of CMTS systems and fiber nodes includes Liva et. al., U.S. Pat. No. 7,149,223; Sucharczuk et. al. US patent application 2007/0189770; and Amit, U.S. Pat. No. 7,197,045. Other prior art includes Sawyer, US patent publication 2003/0066087; Lind, US patent publication 2004/0244043; Cooper, US patent publication 2007/0223512; Civanlar US patent publication 2003/0033379; Kenny, US patent publication 2004/0141747; and Pal US patent publication 2003/0200336.
Typically, nearly all CATV users want immediate access to at least a standard set of cable television channels, and thus to satisfy this basic expectation, usually all CATV cables will receive a basic set of television channels that correspond to this “basic” or “standard” package (which may include various commonly used premium channels as well). Additionally, most users will wish access to a wide range of individualized data, and here the limited bandwidth of the CATV cable starts to become more of a nuisance.
As a first step towards more efficient cable utilization, analog television has been phased out, freeing much FDM bandwidth (analog standard definition TV channels) that can be replaced by more efficient QAM channels carrying both digital TV and DOCSIS data. However phasing out old-fashioned FDM TV signals, although freeing up additional cable bandwidth, has at most satisfied the ever increasing household demand for digital TV and DOCSIS services (data) for only a few years. Thus additional methods to supply a greater amount of data, in particular on-demand video data, voice over IP data, broadband Internet (IP) data, and other data, are desirable.
Terminology Often Used in the Art:
Access points: Access points are typically network connecting devices that allow other devices to connect to a network. Thus for example, an optical fiber node can be viewed as being a type of access point.
Data planes and Control planes: Generally data that is transported over a network can comprise payload data, which is typically data that has utility to the end user. This end user or payload data can be video data, audio data, end user messages, and the like. Another type of data that is transported over the network is not end user data, but is rather used to control the function of the network. This control data can be internal network routing and network configuration data, and the like. These various types of user/payload data and network control/configuration data are occasionally referred to informally as “planes”, although of course the different data types will typically travel through the same communications media. Thus, for example, end user or payload data will be referred to as “the data plane”, while network control and configuration data may be referred to informally as “the control plane”. Occasionally, the term “management plane” will also be used, and this will typically refer to a subset of the “control plane” signals used to carry certain types of network operations and administration traffic not otherwise covered by “the control plane”. Irrespective of choice of nomenclature, however, what is important is that some data is used for end user or payload data, and some data is used to control network operations.
“Converged Cable Access Platform” (CCAP). The term “Converged Cable Access Platform” (abbreviated as CCAP), appears to be a relatively recent, 2011 era, term. For example, the first draft of Cable Television Laboratories, Inc. (CableLabs) publication CM-TR-CMAP-V01-101222 released Dec. 22, 2010 uses the term “CMAP” for “converged multiservice access platform” to discuss their proposed “CMAP Architecture Technical Report”. However in the second draft of the CableLabs report, “Converged Cable Access Platform Architecture Technical Report” CM-TR-CCAP-V02-110614, released Jun. 14, 2011, the term “CMAP” was dropped, and a newer term “Converged Cable Access Platform” (CCAP) appears. However these reports still only taught placing QAM modulators at the head end, rather than at the optical fiber node.
The first use of the term “Converged Cable Access Platform” in the US patent literature appears to be Finkelstein et. al., U.S. patent application Ser. No. 13/297,211, “Converged Cable Access Platform for Provision of Video and Data Services”, filed Nov. 15, 2011, and assigned to Harmonic Inc. The abstract of U.S. patent application Ser. No. 13/297,211 refers to the concept as: “The deep-modulation CCAP architecture includes a remote conversion unit (e.g., that includes one or more modulators and demodulators to perform signal modulation and demodulation) connected to a CCAP core through a digital optical medium (e.g., an optical fiber) to achieve higher network capacity as well as cost and power consumption reduction”.
Computer processors: Generally computer processors (e.g. microprocessors, microcontrollers, and the like) operate by using various registers or memory addresses to hold data, and the processor then operates on this data using various instructions, which may write data to a register, read data from a register, or otherwise alter the contents of a register. Thus for example, commands to a computer processor are typically executed by at least some register reads and writes. Indeed, it is difficult to conceive of a scheme in which commands to a computer processor would not be executed by at least some register reads and writes. Other common processor operations traditionally used to execute various software programs or commands include other register contents altering operations such as AND, OR, IF, rotation, shift, masking, and other commands, commonly known in the art.
Spectrum: spectrum is commonly defined in physics as an array of entities such as light waves (or radio waves) ordered according to their various physical properties such as wavelength. Within the context of a typical HFC system, when the distribution of different channels, such as QAM channels changes, this change can also be said to be changes in the spectrum of RF signals carried by the HFC system. Similarly a mechanism or device that changes the distribution of different channels, such as QAM channels, can be considered to be a spectrum management or allocation device that changes the spectrum produced by a given device.